Re: i_version vs iversion (Was: Re: [RFC PATCH v2 1/2] Btrfs: add noi_version option to disable MS_I_VERSION)

[Dave Chinner <david@fromorbit.com>]

On Wed, Jun 24, 2015 at 07:17:50PM -0400, Theodore Ts'o wrote:
> On Wed, Jun 24, 2015 at 08:02:15PM +0200, David Sterba wrote:
> > 
> > This sounds similar to what Dave proposed, a per-inode I_VERSION
> > attribute that can be changed through chattr. Though the negated meaning
> > of the flag could be confusing, I had to reread the paragraph again.
> 
> Dave did not specify an I_VERSION attribute that would be stored on
> disk.  Instead he talked about a inode flag that would be set when the
> struct inode is created by the file system.

Right.

> This would allow file systems to permanently configure (on a per-inode
> basis) whether or not a particular inode would require a forced
> i_version update any time the inode's data or metadata is modified.  I
> suppose you could initialized the inode flag from an on-disk
> attribute, but that wasn't implied by Dave's proposal, at least as I
> understood it.

It enables filesystems to do this. If btrfs want to add an on-disk
flag to turn off I_VERSION on a per-inode basis, or imply it from
some other on-disk flag, then they are welcome to do so and the
above infrastructure change will support it.

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com